I ate a fleishig dinner. Half an hour later, I was making my milchig lunch for the next day and without thinking I ate a few little strips of cheese from it. What can I do now? How can I do teshuva for this? I feel awfull about it
We all make mistakes, and because HKB”H knows that we are humans, He gave us a way to do teshuva. There are three parts to teshuva, “charta”-regret for what you did, “vidui” to verbally express the sin to HKB”H, and “kabala al ha’asid” to accept on yourself to be better in the future.
The first part you already did because you feel terrible about it, now you should verbally express t to HKB”H, (quietly- no one else has to know about it). Then for “kabala al ha’asid” try to do something that will help you that you should make this mistake again. Learning the halachos puts the mitzvah in the front of our mind and will help that it shouldn’t happen again. You can lean it in whatever way is best for you. You can learn it either from a sefer, an English book, a shiur, or any other way that you are comfortable with, as long as you learn it and spend time on the subject, to help reinforce it.
May HKB:H send you siyata dishmaya that you shouldn’t make any more mistakes.